Oh boy, are we having fun now, or what? First of all, I double checked the figures I supplied and they are good. Striider, please remind me of your panel configuration. Bergmanj, the points you make about aluminum wire are true, but I will offer that, having made and also disassembled many many underwater splices, I would be very hesitant to attempt to run aluminum wires down to a submersible pump. Almost every underwater splice that I have ever disassembled shows signs of leakage. They can be done perfectly so as not to leak but it's not easy or a given. When these splices leak the conductors are usually corroded at least up to the static water level in the well. I would not trust that the aluminum would stay dry down there. Thank you DanG for the information on equivalent gauges for parallel conductors, if you run parallel conductors clear to the pump, as you say Striider, what does that splice look like? Very hard to seal that one. So, all that being what it is, if you take a look at your well report, static level is 200 feet, recommended pump depth 350 feet, and you are in a plastic sleeve (casing) below 41 feet, so how about you make whatever splice you are suggesting above the water level, leaving you about 170 feet of 10/2 with ground leading down to the pump. If you set that splice 250' from your power supply you can even use two of the 12/4 runs to it. Resistance in series is additive. That underwater splice is doable and the other can be soldered above the static level, tape the heck out of it and have some confidence that the plastic casing will not chafe through your tape. I would never do this kind of thing on a jobsite, but it's your thing. Also for down well, especially if you will splice a pump to it, I do not like UF at all. If you do use it, solder the solid #10s into the crimp sleeves. Solid wire does not crimp splice well and is hard to work with. This is all why I come back to panel configuration. IF you can supply 120 vdc it would seem so much easier.
Best,
Damian